Prediction of Thermal Fatigue Life of Lead-Free BGA Solder Joints by Finite Element Analysis

Shin, Young-Eui; Lee, Kyung-Woo; Chang, Kyong-Ho; Jung, Seung-Boo; Jung, Jae Pil

doi:10.2320/matertrans.42.809

Cited by 10 publications

(8 citation statements)

References 6 publications

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“…Additionally, the variability seen amongst the various observed specimens indicates that the shape, real joint area and/or other properties of the solder joints produced by the reflow and assembly processes may have been somewhat inconsistent, even though the initial volume of each solder ball was the same. Other work has shown that thermal fatigue life is affected by the shape of the solder joints 21,22) and the thickness and nature of the diffusion layers that form near the interface. 23,24) Comparison of the micrographs in Figs.…”

Section: Resultsmentioning

confidence: 99%

Improvement of Board Level Reliability for μBGA Solder Joints Using Underfill

2003

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The underfilling BGA as an alternative to direct chip attachment for high density packaging technologies have been developed. This paper discusses the thermomechanical and metallurgical effects of underfill material and the resulting improvement in board level reliability for underfilled BGA assemblies. Finite element analysis (FEA) models were developed to predict the thermal fatigue life of the solder joints during thermal cycling tests for BGA assemblies without and with underfill material. FEA predicted that the stress concentrated in the solder at the crevice between the solder ball and upper substrate was approximately 60 percent of the stress without underfill. Subsequently, the predicted fatigue life was as much as 10 times higher for the underfilled assemblies. The thermal fatigue failure of BGA solder joints was also investigated experimentally using thermal cycle testing with subsequent solder joint analysis by scanning electron microscope (SEM) and energy dispersive X-ray (EDX). The experiments revealed that solder joint failure was caused by propagation of cracks that initiated in the solder at the upper interface between the solder ball and copper pad. The fatigue life of the underfilled assemblies was about 8 times that of the assemblies without underfill. The results showed that the underfill material can play an important role in improving board level reliability for BGA solder joints in harsh environments.

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Section: Resultsmentioning

confidence: 99%

Improvement of Board Level Reliability for μBGA Solder Joints Using Underfill

2003

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“…Figure 7 shows the relationship of m 0 , k, which are investigated with specimens after aging at 120 C for 21 d, and the thermal fatigue life in Sn-37Pb, Sn-3.5Ag and Sn-3.5Ag-0.7Cu. 6) For m 0 and k, the reciprocals are shown in the figure because the solder with low m 0 and k have the excellent thermal fatigue life. Each value shown in Fig.…”

Section: Strain Rate Sensitivity Index Of Lead-free Soldersmentioning

confidence: 99%

“…Generally, the thermal fatigue resistance of the solder depends on solder composition, 6,24,25) thermal cycle conditions, 6,16,29) design of joints 6) and so on. Such specifications alter a plastic strain range applied in the solder joint, and consequently the thermal fatigue resistance of the solder changes according to modified Coffin-Manson equation.…”

Section: Strain Rate Sensitivity Index Of Lead-free Soldersmentioning

confidence: 99%

“…7 is normalized by the datum of the Sn-37Pb solder. For the thermal fatigue life, the data of CSP solder joints 6) were used. Since there were no data of the thermal fatigue lives evaluated by the same thermal cycle test using fine pitch solder joints with other lead-free solders, the comparison could not be conducted with other lead-free solders.…”

Section: Strain Rate Sensitivity Index Of Lead-free Soldersmentioning

confidence: 99%

“…Thus, many studies have been conducted in order to predict the thermal fatigue life of the lead-free solder joint based on the Coffin-Manson equation. 6,7) Some studies conducted on the relationship between the thermal fatigue resistance and the mechanical properties of the solders 8,9) and it was clarified that the creep properties is very important factor in the thermal fatigue resistance of the solder. In particular, it was reported the ranking of the steady state creep rate at the same stress in several lead-free solders does not change in the creep rate ranging from 10 À6 to 10 À3 s À1 .…”

Section: Introductionmentioning

confidence: 99%

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Estimation of Thermal Fatigue Resistances of Sn–Ag and Sn–Ag–Cu Lead-Free Solders Using Strain Rate Sensitivity Index

2005

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A tensile test was conducted to evaluate thermal fatigue resistances of Sn-Ag and several Sn-Ag-Cu lead-free solder alloys. The test is based on the strain rate change method to obtain a strain rate sensitivity index, m. The m values were investigated at various strains during the tensile test until fracture. The plots of m and strain where m is measured showed a linear relationship. Therefore, the m value at zero strain, m 0 , and the gradient of the fitting line, k, were obtained by extrapolation. Using m 0 and k values investigated, an estimation of the thermal fatigue resistance of the solder joint was attempted. The ranking of the reciprocals of m 0 and k in the solders is relatively in good agreement with that of the thermal fatigue resistance of the solder joints, and thus m 0 and k can be indexes to develop a new lead-free solder with the excellent thermal fatigue resistance. Moreover, the influences of the aging treatment on m 0 , k and the microstructure of the solder were also investigated.

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Microstructures and degradation of heat sink very-thin quad flat package no-leads Pb-free Sn-Ag-Cu solder joints after thermal aging

Fredriksz

2005

Journal of Elec Materi

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Heat sink very-thin quad flat package no-leads (HVQFN) packages soldered with Sn-3.8Ag-0.7Cu on metallized laminate substrates have been put to thermal aging. Temperatures from 140°C to 200°C for times up to 30 weeks were applied. The solder joint microstructure develops intermetallic compound layers and voids within the solder. Due to this, the mechanical reliability of the HVQFN inner lead solder joints is degraded. The intermetallic layers are of the type (Cu,Y) 6 Sn 5 , with Y ϭ Ni, Au or Ni ϩ Au, as well as Cu 3 Sn, and follow a power law with aging time: X ϭ C·t n , where n ϭ 0.4 to 1.9 depending on temperature. The voids within the solder are attributed to Sn depletion of the solder in favor of the growth of (Cu,Ni) 6 Sn 5 . They are more pronounced the less the solder volume is in proportion to the intermetallic diffusion area. The amount of voids is quantified as a percentage of the residual solder. The time to reach the failure criterion of 50%, i.e., t 50% , is related to the absolute temperature according to an Arrhenius equation with an activation energy E a ϭ 0.95 eV. This equation is used for determination of the maximum allowable temperature at a certain required operating lifetime.

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Prediction of Thermal Fatigue Life of Lead-Free BGA Solder Joints by Finite Element Analysis

Cited by 10 publications

References 6 publications

Improvement of Board Level Reliability for μBGA Solder Joints Using Underfill

Improvement of Board Level Reliability for μBGA Solder Joints Using Underfill

Estimation of Thermal Fatigue Resistances of Sn–Ag and Sn–Ag–Cu Lead-Free Solders Using Strain Rate Sensitivity Index

Microstructures and degradation of heat sink very-thin quad flat package no-leads Pb-free Sn-Ag-Cu solder joints after thermal aging

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Prediction of Thermal Fatigue Life of Lead-Free BGA Solder Joints by Finite Element Analysis

Cited by 10 publications

References 6 publications

Improvement of Board Level Reliability for &mu;BGA Solder Joints Using Underfill

Improvement of Board Level Reliability for &mu;BGA Solder Joints Using Underfill

Estimation of Thermal Fatigue Resistances of Sn&ndash;Ag and Sn&ndash;Ag&ndash;Cu Lead-Free Solders Using Strain Rate Sensitivity Index

Microstructures and degradation of heat sink very-thin quad flat package no-leads Pb-free Sn-Ag-Cu solder joints after thermal aging

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Improvement of Board Level Reliability for μBGA Solder Joints Using Underfill

Improvement of Board Level Reliability for μBGA Solder Joints Using Underfill

Estimation of Thermal Fatigue Resistances of Sn–Ag and Sn–Ag–Cu Lead-Free Solders Using Strain Rate Sensitivity Index